Aqueous slurry blasting explosive containing silicon and an aeration agent



June 25, 1968 H. R. FEE ET AL 3,390,028

AQUEOUS SLURRY BLASTING EXPLOSIVE CONTAINING SILICON AND AN AERATIONAGENT Filed Jan. 4, 1967 0 A9H3N3 NOOHS HARRY R. FEE ROBERT W. LAWRENCEORIN W. MARKS INVENTORS AGENT United States Patent 3,390,028 AQUEOUSSLURRY BLASTING EXPLOSIVE CONTAINING SILICON AND AN AERA- TION AGENTHarry R. Fee, Hopatcong, N.J., and Robert W. Lawrence and Orin W. Marks,Wilmington, Del., assignors to Hercules Incorporated, Wilmington, Del.,a corporation of Delaware Filed Jan. 4, 1967, Ser. No. 607,260 Claims.(Cl. 149-39) ABSTRACT OF THE DISCLOSURE An aqueous slurry blastingcomposition having an explosive sensitizer and containing silicon and anaeration agent. The aeration agent lowers the maximum specific gravityof the composition at the time of blasting.

This invention relates to aqueous slurry blasting explosives and moreparticularly to an improved aqueous slurry blasting explosive utilizinga metal fuel.

The use of metals as fuels to increase the energy of explosivecompositions has for years been known throughout the art. Of the metalsutilized, aluminum has been one of the metals most Widely used due toits ability to enter the explosive reaction. However, the use ofaluminum in aqueous slurry blasting explosives has certain undesirablecharacteristics including that of high cost as compared to the presentinvention. This will be more readily appreciated from the following.

As previously pointed out, the prior art in the preparation of aqueousslurry blasting agents or explosives containing metals is well known.The use of fine, or mixtures of coarse and fine aluminum in combinationwith explosive ingredients has been demonstrated. The use of finealuminum in connection with ammonium nitrate and water to the exclusionof explosive ingredients has also been demonstrated. In these cases thefineness of the aluminum was important to the operability of thecompositions. In the presence of fine aluminum other metallicingredients were also claimed to be useful. The use of fine aluminumintroduced distinct disadvantages in that fine aluminum contributed tothe hazard of dust explosions. In addition, the reaction betweenammonium nitrate solutions and fine aluminum with evolution of hydrogenwas encountered and special buffering and stabilizers were oftennecessary.

In other teachings in the addition of fine ingredients (200 microns orless), the absence of dissolved fuels was usually required. Inherent inthe use of all fine ingredients is the cap sensitivity of suchcompositions, which in some instances is desirable depending onconditions of use while in other instances is undesirable, such as,where large quantities of slurry explosive are being bulk delivered toblasting sites. In addition, excluding dissolved fuels eliminates manyof the most convenient fuels such as the glycols and the carbohydrates,some of which may be handled as liquids. The use of soluble fuels isalso desirable in bulk delivered slurries because they do not add to thesolids-to-liquid ratio. Additional advantages in using a soluble fuelwill become evident in the examples to follow.

Furthermore, in order to avoid the problems inherent in using finealuminum, other forms were tried. It was observed that flaked and balledaluminum would contribute a measure of sensitivity to the compositions(as contrasted 3,390,028 Patented June 25, 1968 with ordinary aluminumfilings, for instance), and it has become common practice to use thisform. Resorting to flaked aluminum has introduced a dilferent set ofproblems. The sensitizing etiect, i.e., the ability to change aninsensitive composition to an explosive composition, of the flakedaluminum apparently results from the entrapment of air and the resultinginclusion of the air in the form of tiny bubbles in the slurry. It hasbeen conjectured that the inclusion of such bubbles in an explosiveserves to provide hot spots which help initiate the compositions (Moder,C. L., The Physics of Fluids, vol. 6, No. 3, page 375, 1963). Oneproblem, therefore, is to maintain the air bubbles in the aqueousenvironment. Attempts have been made to solve this problem by coatingthe aluminum with hydrophobic material in a separate operation. The useof boron and magnesium has also been claimed to be effective aftertreatment which, of course, entails additional expense to the alreadyexpensive metal ingredient. A further disadvantage to flaked aluminum isthe excessive thickening imparted when high energy compositions arerequired and the aluminum content is increased or the water content islowered.

The primary object of the present invention is, therefore, to provideaqueous slurry blasting explosives which while being at least asenergetic as convetnional metallized slurries, eliminate the shortcomings and disadvantages outlined above.

Other objects of the invention will appear hereinafter the novelfeatures and combinations being set forth in the appended claims.

Generally described, the present invention contemplates an aqueousslurry blasting explosive comprising inorganic oxidizingsalt, explosivesensitizing agent, particulate silicon, thickener, and an aeration agentpresent in an amount to lower the maximum specific gravity of theaqueous slurry blasting explosive to between about 30 and of the maximumat the time of blasting.

Examples for operation of the invention are given as well as an examplefor preparing an aluminized aqueous slurry for comparison of the endproducts. In these exam ples parts are by weight unless otherwiseindicated. Examples l and 2 contained no silicon, Example 3 containedsilicon, Example 4 contained aluminum and Example 5 contained siliconWithout an aeration agent. These examples are given in Table I and wereprepared as follows:

EXAMPLE 1 1. Combine the pine oil, AN and SN with the water of solution(hot) and heat to F.

2. Mix the smokeless powder into the solution.

3. Adjust the pH to between 4.5 and 5.0 with acetic acid.

4. Disperse the guar gum in about 3 times its weight of ethylene glycoland mix into the solution.

5. Disperse the guar gum cross-linking agent in the remaining glycol andmix into the solution.

EXAMPLES 2, 3, 4 AND 5 Steps 1, 2, 3 and 4 are the same as for Example 1except that pine oil is omitted in Step 1 and the silicon or alumi numare also added in Step 2.

Step 5.Disperse the sodium nitrite in about 3 /2 times its weight ofwater and add to the mix.

Step 6.--Disperse the guar gum cross-linking agent in the glycolremaining from Step 4 and mix into the solution.

TABLE Example No .1

Components:

Silicon type II Aluminum Granules (90% on 100 mesh) Water i'. AmmoniumNitrate, prills Sodium Nitrate, prills Ground Smokeless Powder. EthyleneGlycol Guar Gum Pine Sodium Nitrite- Oxygen Balance, percent. FEE], 24Hour Specific, Gravity. p Detonation Rate, M/S..- Pipe Diameter, in

.ll. 0 1. ll.

ar-i- Slurry Temperature, F l0 l3 Underwater Measured Energy WeightBasis,

Relative to Confined 60% HP Gel:

Shock Energy l. 58 l. 78 l. 95 ll. 87 ll. 51 Thrust Energy ll. 71 l. 86l. 94 ill. 92 l. 69

Maximum.

All of the gj Shawn in ,Table I tested, TABLE II.SILICON PARTICLE srznsAND PURITY x o r o eton'atlon rate W 1 e connne e pl slve ene gy an r guType 1 1 1 11 underwater. Detonation rates were measured over a lengthof cm. and were recorded on a counter chronograph. The underwater thrusti bubble) and shock energies were determined in the manner indicated byCole (Cole, H.D., Underwater Explosions, Princeton University Press.Princeton, New Jersey {1948), pages 228 to 285) and as reported bySadwin (Sadwin, L. D, Cooley, C. M., Porter, S. J., Stresau, R. H.;Underwater Evaluation of the Performance of Explosives, InternationalSymposium on Mining Research, Missouri, February i961, vol. l) and hiscollaborators with some minor modifications.

The data are reported relative to confined 60% HP Gel. The charges, 20lbs. to lbs. in weight, are confined in 5-inch diameter by 28-inch longblack iron pipe. The pipes are suspended vertically, l2 feet below thesurface of the water to the charge center, and 28 feet from the bottomof the pond. The charges were initiated from the bottom with XC-49Pentolite boosters [/50 PETN/TNT), 3-inch diameter by l-inch high and190 grams in weight. The pressures generated by the detonations weresensed by piezoelectric hydrophone transducers and were recorded on anoscilloscope. The bubble times were also sensed by the transducers andwere recorded on the oscilloscope.

With reference to the examples and Table I, it will be seen asgraphically presented in the attached drawing in linear form, that theshock energy and the thrust energy for the silicon compositions washigher than that for the aluminum. It was most surprising to discover,however, that the composition of Example 5 containing 14% siliconwithout aeration had shock and thrust energy values about equal to onlythat of Example 1 containing no metal or aeration. Thus, the improvementand importance in utilizing an aeration agent with silicon containingcompositions may be fully appreciated. Although silicon is shown in theexamples in an amount of 14% which represents a practical amount inaqueous slurry explosive compositions, the amount of silicon useddepends primarily upon the explosive energy required but as a practicallimit would start at about 3 and not ordinarily exceed 30% with fromabout 3 to about 20% being preferred. Typical particle size distributionand purity of preferred silicons are shown in Table II. The silicondesignated Si II was used in the examples. In the operation of thisinvention, particle size and purity are not critical. This permits theuse of economical technical grades of alloys and blends thereof. It willbe further appreciated, however, that finely divided silicon can be usedin accordance with this invention tree from the hazard of flammabilityas compared to that of finely divided aluminum, as shown in Table III.

82% smaller than 74 microns.

Do 325 Through 325 39% smaller than 44 microns.

i Sharples Micromerograph" particle size distribution analysis.

TYPICAL ASSAY OF SILICON Types I and 111 Type 11 Percent Silicon 85Silicon type II is a preferred material due to its ability to enter theexplosive reaction and its economy. Type II is a silicon alloy blendaveraging about 85% silicon, with a nominal silicon range of 82 to 88%.The range analysis of major residual elements bound in the alloy is asfollows:

Silicon types I and III are silicon alloys containing to 97% silicon andhaving a range analysis of major residual elements bound in the alloy asfollows:

Aluminum 0.20-0.65 Calcium 0.02-0.05 Carbon 0.04-0.09 IChromium0.01-0.03 Copper 0.01-0.03 Nickel 0.035-0.06 Titanium 0.03-0.07Phosphorous 0002-0006 Sulfur 0.060.10 Vanadium 0.06-0.10 Manganese0.01-0.03 llron 0.5-1.5

TABLE III.DUST FLAMMABILITY TESTS Paint grade aluminum (97% 74 microns)Tests were conducted by dropping approximately 100 grams of sample,about 16 inches down an 8-inch diameter tubejiventilated at the bottomand open at the top and simultaneously initiating an electric squib.

The inorganic oxidizing salts are shown in the examples pertaining tosilicon as being present in amount of 40.6% of the compositions. Ifrequirements so dictate, these salts could comprise between about 25 and75% of the compositions. The physical form of the salts is not critical,coarse or fine, or mixtures of coarse and fine prilled and/ or granularto powdery material all being suitable. In fact, in some preferredapplications of this invention, the oxidizing salts are introduced intothe compositions as an aqueous solution. Ammonium nitrate (A.N.),because of its availability, is the preferred oxidizing salt but sodiumnitrate (S.N.) in practice almost always makes up a portion of theoxidizing salts, preferably to the extent of about to 25% of thecomposition but 0% to about 30% may be used. Although the examples givenare all formulated with inorganic nitrates, the use of other inorganicoxidizing salts are within the scope of this invention. For instance,various of the alkali or alkaline earth nitrates may be used for all ora portion of the A.N., but in practice, not more than about 80 of theA.N. would be so substituted. A preferred range for the presence of A.N.is from about 20 to about 50%. In addition, salts selected from thepercholorates, such as, ammonium, sodium and potassium percholorate maybe used.

The explosive sensitizing agent, smokeless powder, appears in theexamples as being present in amount of 25% of the compositions. Where areduction in the critical diameter is desired or where the availabilityof the sensitizing agent is particularly convenient up to about 50% maybe utilized as a practical maximum. Generally, however, about 10 to 40%will be present. Other suitable sensitizing agents include TNT, RDX,HMX, PETN, Pentolite, Cyclotol, HBX and the like. These materials may bepelleted, flaked or grained.

The non-explosive carbonaceous fuel, ethylene glycol, appears in theexamples as being present in amount of 2.5% of the compositions.Depending upon the conditions, 0 to about of the compositions may bemade up of one or more carbonaceous fuels, but a maximum of about 7% ismore commonly used. Where insoluble carbonaceous fuel or immisciblecarbonaceous liquids are used, they must, of course, be suspended in ordispersed throughout the aqueous phase.

Water is shown as 17% by weight of the compositions in the examples.Between about 10 and 30% of the compositions may be composed of waterbut in conventional practice about 14 to 24% is more commonly employed.

It will be appreciated that the compositions of this invention arecomposed of a blend of liquid and solid components. It is essential thatthe solid phase (or non-homogeneous liquid phase, when such is utilized)be evenly dispersed throughout the liquid phase. This is accomplished byemploying thickening agents which retard or arrest the settling of thesolid material. Suitable thickeners include carboxymethylcellulose,methyl cellulose, water soluble starches, cereal flour and the like.Preferred practice is to employ guar gum and to cross-link (gel) the gumwith a suitable cross-linking agent. The cross-linking agent may becombined with the gum and is commercially available in such form or maybe added as a separate ingredient in very small amounts, usually lessthan 0.1% of the total composition. The gum may be used in as low amountas 0.4% or thereabouts and up to about 4%, but more generally about 0.7%to 1.8% is used.

Furthermore, it will be appreciated that the specific gravity of thecompositions of this invention at the time of blasting is important. Aspecific gravity of between about 30 and 95% of the maximum specificgravity of the aqueous slurry blasting explosives and preferably betweenabout 50 and at the time of blasting has been found to enhance theexplosive energy of the compositions of this invention. The adjustmentand maintenance of the compositions to the specific gravities givenabove are accomplished by incorporation of an aeration agent into thecomposition. The term an aeration agent as used herein means an agentwhich causes the composition to be combined with or charged with gas.The term maximum specific gravity as used herein means the specificgravity of the aqueous slurry blasting explosive exclusive of gas.

As is discussed in the reference previously given, the presence of smallevenly dispersed air or gas bubbles throughout an explosive can bebeneficial to initiation and propagation. The operation of thisembodiment is in accord with the aforementioned hot spot theory andencompasses the inclusion of small amounts of tiny gas bubblesthroughout the liquid phase. Examples of this type of composition aregiven in Table I where sodium nitrite is used as the aeration agent inamount of 0.065%. Also, gas bubbles may be generated as disclosed byFerguson et al. (US. 3,288,658) and Swisstack (US. 3,288,661). However,a particularly eflicacious aeration agent for use in lowering andmaintaining specific gravities in accordance with this invention issodium nitrite in an amount of from about 0.01 to about 0.2% by weightof the blasting composition. As demonstrated in the examples and thedrawing, this aeration agent present in the small amount of 0.065% gavefinal 24 hour specific gravities of about 1.25-1.35 at a pH of 4.5-4.9and gave extremely improved and surprising performance of the aeratedsilicon containing composition in respect to detonation rate, shockenergy, and thrust energy.

It is evident that the inclusion of various minor ingredients is withinthe scope of this invention. Adjustments are routinely made withappropriate acids and bases to obtain desired pH ranges. Othervariations and modifications are apparent to those versed in the art andthe examples given are not intended to nor do they represent limits onthe scope of this invention.

The advantages of the invention are multifold. Unlike some conventionalcompositions the use of fine easily flammable and overly reactivemetallic sensitizers is not required. Where it is convenient ordesirable to use the energetic metal fuel com ponent partially in thefine particulate form, the compositions of the invention represent agreat improvement through a decreased susceptibility to dust explosions.No special bufiering is required for the compositions of this inventionother than the normal pH adjustments. The form of the metallic energizerwhether chemically pure or technical grade is not critical in thesecompositions and no special treatment of the energizer component isnecessary, thus providing improved economy. Through the availability ofthese compositions it will be possible to obtain the explosive energy ofconventional compositions while avoiding their shortcomings anddisadvantages.

It will be seen, therefore, that this invention may be carried out bythe use of various modification and changes without departing from itsspirit and scope with only such limitations placed thereon as areimposed by the appended claims.

What we claim and desire to protect by Letters Patent are:

1. An aqueous slurry blasting explosive comprising inorganic oxidizingsalt, self-explosive sensitizing agent, particulate silicon, water,thickener, and an aeration agent present in an amount to providesufl'lcient air or gas bubbles to lower the maximum specific gravity ofthe wzrasopzs ii aqueous slurry blasting explosive to between about 30and 95% of the maximum.

2. The aqueous slurry blasting explosive of claim 1 wherein the siliconis present in an amount of from about 3 to about 30% by weight.

3. The aqueous slurry blasting explosive of claim 2 wherein the siliconis present as a silicon alloy containing from about 80 to about 97%silicon by weight of said alloy.

4. The aqueous blasting explosive of claim 2 wherein the silicon ispresent as a mixture of silicon alloys containing from about 80 to about97% silicon by weight of said mixture.

5. An aqueous slurry blasting explosive comprising from about 20 toabout 50% ammonium nitrate, from about 5 to about 25% of sodium nitrate,from about 10 to 50% of self-explosive sensitizing agent, from about 3to about 20% of particulate silicon, from to about 15% of carbonaceousfuel, from about 0.4 to about 4% of thickening agent, from about 10 toabout 30% of water, all percentages by weight, and an aeration agentpresent in an amount to provide sufiicient air or gas bubbles to lowerthe maximum specific gravity of the aqueous slurry blasting explosive tobetween about 50 and 90% of the maximum.

6. The aqueous slurry blasting explosive of claim 5 wherein the siliconis present as a silicon alloy containing from about 80 to about 97%silicon by weight of said alloy.

7. The aqueous slurry blasting explosive of claim 5 wherein the siliconis present as a mixture or silicon alloys containing from about 80 toabout 97% silicon by Weight of said mixture.

18. An aqueous slurry blasting explosive comprising by weight from about20 to about 50% ammonium nitrate, from about 5 to about of sodiumnitrate, from'about l0 to of self-explosive sensitizing agent, fromabout .3 to 20% of particulate silicon alloy mixture containing about to97% silicon by weight, from 0 to about 15% of carbonaceous fuel, fromabout 0.4 to about 4% of thickening agent, from about 10 to about 30% ofwater, and from about 0.01 to about 0.2 of sodium nitrite as an aerationagent to provide sufficient gas bubbles to lower and maintain themaximum specific gravity of the aqueous slurry blasting explosive tobetween about 50 and of the maximum.

F9. The aqueous slurry blasting explosive of claim 8 wherein thesensitizing agent is smokeless powder.

10. The aqueous slurry blasting agent of claim 8 wherein the sensitizingagent is trinitrotoluene.

References Cited UNITED STATES PATENTS 3,164,503 11/1965 Gehrig 149-60 X13,249,474 15/1966 Clay et al. 14944 X 3,288,661 ll/1966 Swisstack 1496013,294,601 l2/1966 Gordon 14960 BENJAMIN R. PADGETT, Primary Examiner.

CARL D. QUARFORTH, Examiner.

5. J. LECHERT, JR., Assistant Examiner.

